* {
    padding: 0;
    margin: 0;
    box-sizing:border-box;
}
body {
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    /*background-image: url(../img/back6.jpeg);*/
    /*background-size: 100% 110%;*/
    /*background-repeat: no-repeat;*/
    background: linear-gradient(#141e30,#243b55);
}
.login {
    display: flex;
    flex-direction: column;
    align-items: center;
    width: 360px;
    padding: 30px;
    background-color: rgba(0, 0, 0, 0.2);
    box-shadow: 0 12px 24px rgba(0,0,0,0.4);
}
.login h3 {
    color: #e4c23a;
    margin-bottom: 24px;
}
.login .login_box {
    position: relative;
    width: 100%;
}
.login .login_box input {
    outline: none;
    border: none;
    width: 100%;
    padding: 9px 0;
    margin-bottom: 24px;
    color: #fff6ee;
    font-size: 16px;
    border-bottom: 1px solid #fff6ee;
    background-color: transparent;
}
.login .login_box label {
    position: absolute;
    top: 0;
    left: 0;
    padding: 9px 0;
    color: #fff6ee;
    pointer-events: none;
    transition: all 0.3s;
}
/* :focus选择器 是当input获得焦点时为触发样式 + 相邻兄弟选择器，会去找该相邻的兄弟选择器，即label*/
/* :valid选择器 是判断input框内输入是否合法，合法才会执行下面的属性代码，判断依据为html中的required*/
.login .login_box input:focus + label,
.login .login_box input:valid + label {
    top: -18px;
    color: #03e9f4;
    font-size: 12px;
}
.login button {
    overflow: hidden;
    position: relative;
    padding: 9px 18px;
    color: #e4c23a;
    border: none;
    background-color: transparent;
    text-decoration: none;
    transition: all 0.5s;
}
.login button:hover {
    color: #002255;
    border-radius: 4px;
    background-color: #03e9f4;
    box-shadow: 0 0 4px #03e9f4,0 0 24px #03e9f4,0 0 48px #03e9f4,0 0 96px #03e9f4;
}
.login button span {
    position: absolute;
}
.login button span:first-child {
    top:0;
    left: -100%;
    width: 100%;
    height: 2px;
    background: linear-gradient(to right,transparent,#03e9f4);
    animation: move1 1s linear infinite;
}
.login button span:nth-child(2) {
    right: 0;
    top: -100%;
    width: 2px;
    height: 100%;
    background: linear-gradient(transparent,#03e9f4);
    animation: move2 1s linear 0.25s infinite;
}
.login button span:nth-child(3) {
    bottom: 0;
    right: -100%;
    width: 100%;
    height: 2px;
    background: linear-gradient(to left,transparent,#03e9f4);
    animation: move3 1s linear 0.5s infinite;
}
.login button span:last-child {
    left: 0;
    bottom: -100%;
    width: 2px;
    height: 100%;
    background: linear-gradient(transparent,#03e9f4);
    animation: move4 1s linear 0.75s infinite;
}
@keyframes move1 {
    0% {
        left: -100%;
    }
    50%,
    100% {
        left: 100%;
    }
}
@keyframes move2 {
    0% {
        top: -100%;
    }
    50%,
    100% {
        top: 100%;
    }
}
@keyframes move3 {
    0% {
        right: -100%;
    }
    50%,
    100% {
        right: 100%;
    }
}
@keyframes move4 {
    0% {
        bottom: -100%;
    }
    50%,
    100% {
        bottom: 100%;
    }
}